1. Field of the Invention
The present invention relates to a method of displacing a honing tool for machining workpiece bores, and includes the steps of initially rapidly displacing the tool until the latter contacts the workpiece, and then changing over to a slower machining displacement. The present invention also relates to an apparatus for carrying out this method. This apparatus has, for the honing tool, a displacement apparatus which provides for a rapid displacement and for a slower machining displacement or stock removal feeding.
2. Description of the Prior Art
In modern honing machines, the honing tool is rapidly displaced until the honing stones contact the workpiece, whereupon the honing tool is changed over to the actual machining displacement speed, which is slower. For this purpose, with one known arrangement of this type (German Offenlegungsschrift No. 20 41 061), a first motor is provided for the rapid displacement, and a second motor is provided for the slower machining displacement.
The changing over from the rapid displacement to the machining displacement or stock removal feeding is effected by a switching mechanism which, by means of a digital sensor, measures the speed of the displacement spindle, in which, when the speed drops off as a result of the braking effect as the honing stones come to rest against the wall of the workpiece bore, stops the high-speed first motor and at the same time starts the second motor, with the lagging of the high-speed motor after being turned off, resulting from its inertia, being absorbed by a resilient connecting member disposed between the motor and the displacement spindle.
This heretofore known arrangement is supposed to reduce the overall working time during honing, and avoid a breaking of the honing stones and damage to the workpieces.
However, this is only inadequately accomplished. Especially with honing tools having a small diameter, damage due to overstressing repeatedly occurs because the speed of the displacement or feeding spindle is reduced only after the honing stones have already been pressed with considerable force against the wall of the workpiece bore.
The reason for this is primarily because during the transmission of the displacement or feeding movement, considerable frictional forces have to be overcome; in particular due to the significant conversion of the axial displacement or feeding movement into a radial movement of the honing stones via a wedge gearing at relatively slight axial forces, large radial displacement forces result which prevent a sensitive "location or cutting of the honing stones". Furthermore, the construction of the heretofore known arrangement, which operates with two displacement motors, is very expensive and complex, and accordingly is, of course, also susceptible to breakdown.
An object of the present invention is to provide a displacement or feeding apparatus of the aforementioned general type which on the one hand has a simple construction and operates reliably, and on the other hand precludes overstressing of the tool and/or the workpiece, even when very small honing diameters are involved.